BOSTON PUBLIC LIBRARY: BOSTON, MASSACHUSETTS

The Boston Public Library is the second largest in the country, at 930,000-square-feet and holding 21 million items — but that’s only part of why it’s so spectacular. The older side of the building, which opened in 1895, features murals by John Singer Sargent, and a courtyard based on the 16th-century Palazzo della Cancelleria in Rome.